The present invention relates to a container for an inhalation anesthetic and a method for storing an inhalation anesthetic. In particular, the present invention is directed to a container constructed from a polymethylpentene material that provides a barrier to vapor transmission through a wall of the container and that is non-reactive with an inhalation anesthetic contained therein.
Fluoroether inhalation anesthetic agents such as sevoflurane (fluoromethyl-2,2,2-trifluoro-1-(tri fluoromethyl)ethyl ether), enflurane (2-chloro-1,1,2-trifluoroethyl difluoromethyl ether), isoflurane (1-chloro-2,2,2-trifluoroethyl difluoromethyl ether), methoxyflurane (2,2-dichloro-1,1-difluoroethyl methyl ether) and desflurane (2-difluoromethyl 1,2,2,2-tetrafluoroethyl ether) are typically distributed in containers constructed of glass. Although these fluoroether agents have been shown to be excellent anesthetic agents, it has been found that under certain conditions the fluoroether agent and the glass container may interact, thereby facilitating degradation of the fluoroether agent. This interaction is believed to result from the presence of Lewis acids in the glass container material. Lewis acids have an empty orbital which can accept an unshared pair of electrons and thereby provide a potential site for reaction with the alpha fluoroether moiety (--C--O--C--F) of the fluoroether agent. Degradation of these fluoroether agents in the presence of a Lewis acid may result in the production of degradation products such as hydrofluoric acid.
The glass material currently used to contain these fluoroether agents is referred to as Type III glass. This material contains silicon dioxide, calcium hydroxide, sodium hydroxide and aluminum oxide. Type III glass provides a barrier to the transmission of vapor through the wall of the container, thereby preventing the transmission of the fluoroether agent therethrough and preventing the transmission of other vapors into the container. However, the aluminum oxide contained in glass materials such as type III glass tend to act as Lewis acids when exposed directly to the fluoroether agent, thereby facilitating degradation of the fluoroether agent. The degradation products produced by this degradation, e.g., hydrofluoric acid, may etch the interior surface of the glass container, thereby exposing additional quantities of aluminum oxide to the fluoroether compound and thereby facilitating further degradation of the fluoroether compound. In some cases, the resulting degradation products may compromise the structural integrity of the glass container.
Efforts have been made to inhibit the reactivity of glass to various chemicals. For example, it has been found that treating glass with sulfur will protect the glass material in some cases. However, it will be appreciated that the presence of sulfur on the surface of a glass container is not acceptable in many applications.
Furthermore, glass containers present a breakage concern. For example, glass containers may break when dropped or otherwise subjected to a sufficient force, either in use or during shipping and handling. Such breakage can cause medical and incidental personnel to be exposed to the contents of the glass container. In this regard, inhalation anesthetic agents evaporate quickly. Thus, if the glass container contains an inhalation anesthetic such as sevoflurane, breakage of the container may necessitate evacuation of the area immediately surrounding the broken container, e.g, an operating room or medical suite.
Efforts to address breakage concerns typically have involved coating the exterior, non-product contact surfaces of the glass with polyvinyl chloride (PVC) or synthetic thermoplastic resin such as Surlyn.RTM. (a registered trademark of E.I. Du Pont De Nemours and Company). These efforts increase the cost of the containers, are not aesthetically pleasing, and do not overcome the above-discussed problems related to degradation which can occur when using glass to contain fluoroether-containing inhalation anesthetic agents.
For these reasons, it is desirable to provide a container constructed from a material other than glass in order to store, transport, and dispense inhalation anesthetics, thereby avoiding the above-discussed shortcomings of glass. The preferred material does not contain Lewis acids which can promote the degradation of the inhalation anesthetic agent, provides a sufficient barrier to vapor transmission into and out of the container, and increases the container's resistance to breakage relative to a glass container.